Magnetic torque of uranium dioxide single crystals*

Uranium dioxide is one of the most studied actinide compounds due to its fundamental and applied importance. Recently, we have performed a low-temperature magnetostriction study of UO₂ in magnetic fields up to 95 T [Nature Comm. 8, 99 (2017)], and uncovered the appearance of linear magnetostriction, leading to a trigonal distortion and piezomagnetism (the first example of piezomagnetism in f-electron spin system). The unusually strong correlations between the magnetic moments in U-atoms and lattice distortions are a direct consequence of the non-collinear symmetry of the magnetic state that breaks time reversal symmetry in a non-trivial way that leads to the piezomagnetism. The microscopic nature of these interactions, however, remains unclear. During the talk, we will present magnetic torque measurements (up to 35 T) performed on oriented UO₂ single crystals. We will discuss implications of these results in the context of the origin of the piezomagnetic ground state in this material.